How do you add a percentage calculator in javascript?

[Shadowhack]

I am working on a shopping cart function in javascript and I want to have the shipping calculated out based on the total price of the sale. Can anyone help me write the code to place it into javascript?

[rragsdaleii]

this is basic panel code so far still yet to complete it, it can only multiply and subtractimport java.awt.*;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.*;public class BasicPanel extends Panel implements ActionListener {private TextField inputOutputField;private String[] strButtonCaptions = {"1", "2", "3", "*", "1/x","4", "5", "6", "/", "x^n","7", "8", "9", "+", "+/-","0", ".", "=", "-", "x!" };private String[] strAxilaryButtonsCaptions = {"CA", "CE", "Round"};private Button[] btnKeys, btnAxilaryKeys;static double numBuffer;//Initialize all unary operators for basic calculatorstatic boolean multiply = false, divide = false, addition = false, subtract = false ;static boolean power = false; public BasicPanel(TextField inputOutputField){this.inputOutputField = inputOutputField;//Set layout of panelthis.setLayout(new BorderLayout());//Create inner panels to aid in layout of componetsPanel northPanel = new Panel();Panel southPanel = new Panel();northPanel.setLayout(new GridLayout(4, 5, 5, 5));southPanel.setLayout(new GridLayout(1, 3, 5, 5));//Set up basic calculator buttonsbtnKeys = new Button[strButtonCaptions.length];//Instinate buttons, add to southPanel, setActionCommand and register event listenerfor(int count = 0; count < strButtonCaptions.length; count++){btnKeys[count] = new Button(strButtonCaptions[count]);northPanel.add(btnKeys[count]);btnKeys[count].setActionCommand(strButtonCaptions[count]);btnKeys[count].addActionListener(this);}btnAxilaryKeys = new Button[strAxilaryButtonsCaptions.length];for(int count = 0; count < strAxilaryButtonsCaptions.length; count++){btnAxilaryKeys[count] = new Button(strAxilaryButtonsCaptions[count]);southPanel.add(btnAxilaryKeys[count]);btnAxilaryKeys[count].addActionListener(this);}//Add panels to main panelthis.add(northPanel, BorderLayout.NORTH);this.add(southPanel, BorderLayout.SOUTH);}public static void resetBinaryOperators(){multiply = false;divide = false;addition = false;subtract = false;power = false;}public String multiply(String operand){String result = "";try{result =Double.toString( (numBuffer * Double.parseDouble(operand)) );}catch(NumberFormatException nfe){result = "Number format exception";}return result;}public String divide(String operand){String result = "";try{result = Double.toString((numBuffer / Double.parseDouble(operand)) );}catch(NumberFormatException nfe){result = "Number format exception";}return result;}public void actionPerformed(ActionEvent e) {String command = e.getActionCommand();String strBuffer = new String(); //Create string buffer to hold text from textfield//Remove default zero from text field if presentif(inputOutputField.getText().equals("0"))s trBuffer = "";elsestrBuffer = inputOutputField.getText(); //Check to see if numeric button was pressed and append to text fieldtry{if((Integer.parseInt(command) >= 0) && (Integer.parseInt(command)